HSBC Branch in Dubai

HSBC is working with law enforcement to catch those behind a cyber attack that forced its personal banking websites in the UK to shutdown, its second major service outage this month, the bank said on Friday.

Europe’s largest lender said it had “successfully defended” its systems against a distributed denial of service (DDoS) attack but it was experiencing fresh threats, impeding full restoration of its services.

HSBC’s internet and mobile services have partially recovered, and we continue to work to restore a full service,

John Hackett, UK Chief Operating Officer, said in a statement.

We are closely monitoring the situation with the authorities

The outage began on Friday morning and online services were still down by 1630 GMT (11:30 a.m. ET).

DDoS attacks are often used by cyber criminals trying to disrupt businesses and companies with significant online activities.

HSBC has declined to estimate when its online services might resume. Its Twitter feed said all major branches will be open on Saturday to help manage urgent transactions.